The Sacramento River is the principal river of Northern California in the United States and is the largest river in California. Rising in the Klamath Mountains, the river flows south for 400 miles (640 km) before reaching the Sacramento–San Joaquin River Delta and San Francisco Bay. The river drains about 26,500 square miles (69,000 km2) in 19 California counties, mostly within the fertile agricultural region bounded by the Coast Ranges and Sierra Nevada known as the Sacramento Valley, but also extending as far as the volcanic plateaus of Northeastern California. Historically, its watershed has reached as far north as south-central Oregon where the now, primarily, endorheic (closed) Goose Lake rarely experiences southerly outflow into the Pit River, the most northerly tributary of the Sacramento.
The Sierra Nevada is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily in Nevada. The Sierra Nevada is part of the American Cordillera, an almost continuous chain of mountain ranges that forms the western "backbone" of the Americas.
The Merced River, in the central part of the U.S. state of California, is a 145-mile (233 km)-long tributary of the San Joaquin River flowing from the Sierra Nevada into the San Joaquin Valley. It is most well known for its swift and steep course through the southern part of Yosemite National Park, where it is the primary watercourse flowing through Yosemite Valley. The river's character changes dramatically once it reaches the plains of the agricultural San Joaquin Valley, where it becomes a slow-moving meandering stream.
The Tuolumne River flows for 149 miles (240 km) through Central California, from the high Sierra Nevada to join the San Joaquin River in the Central Valley. Originating at over 8,000 feet (2,400 m) above sea level in Yosemite National Park, the Tuolumne drains a rugged watershed of 1,958 square miles (5,070 km2), carving a series of canyons through the western slope of the Sierra. While the upper Tuolumne is a fast-flowing mountain stream, the lower river crosses a broad, fertile and extensively cultivated alluvial plain. Like most other central California rivers, the Tuolumne is dammed multiple times for irrigation and the generation of hydroelectricity.
Pineapple Express is a specific recurring atmospheric river both in the waters immediately northeast of the Hawaiian Islands and extending northeast to any location along the Pacific coast of North America. It is a non-technical term and a meteorological phenomenon. It is characterized by a strong and persistent large-scale flow of warm moist air, and the associated heavy precipitation. A Pineapple Express is an example of an atmospheric river, which is a more general term for such relatively narrow corridors of enhanced water vapor transport at mid-latitudes around the world.
The Feather River is the principal tributary of the Sacramento River, in the Sacramento Valley of Northern California. The river's main stem is about 73 miles (117 km) long. Its length to its most distant headwater tributary is just over 210 miles (340 km). The main stem Feather River begins in Lake Oroville, where its four long tributary forks join—the South Fork, Middle Fork, North Fork, and West Branch Feather Rivers. These and other tributaries drain part of the northern Sierra Nevada, and the extreme southern Cascades, as well as a small portion of the Sacramento Valley. The total drainage basin is about 6,200 square miles (16,000 km2), with approximately 3,604 square miles (9,330 km2) above Lake Oroville.
Oroville Dam is an earthfill embankment dam on the Feather River east of the city of Oroville, California, in the Sierra Nevada foothills east of the Sacramento Valley. At 770 feet (235 m) high, it is the tallest dam in the U.S. and serves mainly for water supply, hydroelectricity generation, and flood control. The dam impounds Lake Oroville, the second-largest reservoir in California, capable of storing more than 3.5 million acre-feet (1.1×10^12 US gal; 4.3×109 m3).
Lake Oroville is a reservoir formed by the Oroville Dam impounding the Feather River, located in Butte County, northern California. The lake is situated 5 miles (8 km) northeast of the city of Oroville, within the Lake Oroville State Recreation Area, in the western foothills of the Sierra Nevada. Known as the second-largest reservoir in California, Lake Oroville is treated as a keystone facility within the California State Water Project by storing water, providing flood control, recreation, freshwater releases to assist in controlling the salinity intrusion into the Sacramento-San Joaquin Delta and protecting fish and wildlife.
The California State Water Project, commonly known as the SWP, is a state water management project in the U.S. state of California under the supervision of the California Department of Water Resources. The SWP is one of the largest public water and power utilities in the world, providing drinking water for more than 27 million people and generating an average of 6,500 GWh of hydroelectricity annually. However, as it is the largest single consumer of power in the state itself, it has a net usage of 5,100 GWh.
Floods in the United States are generally caused by excessive rainfall, excessive snowmelt, and dam failure. Below is a list of flood events that were of significant impact to the country during the 20th century, from 1900 through 1999, inclusive.
Folsom Dam is a concrete gravity dam on the American River of Northern California in the United States, about 25 mi (40 km) northeast of Sacramento. The dam is 340 ft (100 m) high and 1,400 ft (430 m) long, flanked by earthen wing dams. It was completed in 1955, and officially opened the following year.
California's interconnected water system serves almost 40 million people and irrigates over 5,680,000 acres (2,300,000 ha) of farmland. As the world's largest, most productive, and potentially most controversial water system, it manages over 40 million acre-feet (49 km3) of water per year. Use of available water averages 50% environmental, 40% agricultural and 10% urban, though this varies considerably by region and between wet and dry years. In wet years, "environmental" water averages 61%, while in dry years it averages 41%, and can be even lower in critically dry years.
Yosemite National Park is located in the central Sierra Nevada of California. Three wilderness areas are adjacent to Yosemite: the Ansel Adams Wilderness to the southeast, the Hoover Wilderness to the northeast, and the Emigrant Wilderness to the north.
The Great Flood of 1862 was the largest flood in the recorded history of California, Oregon, and Nevada, inundating the western United States and portions of British Columbia and Mexico. It was preceded by weeks of continuous rains and snows that began in Oregon in November 1861 and continued into January 1862. This was followed by a record amount of rain from January 9–12, and contributed to a flood that extended from the Columbia River southward in western Oregon, and through California to San Diego, as well as extending as far inland as the Washington Territory, the Utah Territory, and the western New Mexico Territory.
The historical and ongoing droughts in California result from various complex meteorological phenomena, some of which are not fully understood by scientists.
Flooding in 2017 affected parts of California in the first half of the year. Northern California saw its wettest winter in almost a century, breaking the record set in 1982–83. The same storm systems also flooded parts of western Nevada and southern Oregon. The damage was estimated at $1.55 billion ($1,926,663,046 today), including damage to California roads and highways estimated at more than $1.05 billion.
In February 2017, heavy rainfall damaged Oroville Dam's main and emergency spillways, prompting the evacuation of more than 180,000 people living downstream along the Feather River and the relocation of a fish hatchery.
The January 2018 American West floods occurred due to heavy precipitation in the Western United States. While wildfires in Southern California exacerbated the rain's effects there, other states, like Nevada, also experienced flooding.
Periods of heavy rainfall caused by multiple atmospheric rivers in California between December 31, 2022, and March 25, 2023, resulted in floods that affected parts of Southern California, the California Central Coast, Northern California and Nevada. The flooding resulted in property damage and at least 22 fatalities. At least 200,000 homes and businesses lost power during the December-January storms and 6,000 individuals were ordered to evacuate.
